Strange power problem with new Asus P4C800 motherboard

Hi,

I've recently decided to upgrade my computer, so amongst other things
I bought a new CPU (2.8GHz P4) and motherboard. After receiving a nice
big box full of computer bits from Dabs I enthusiastically set about
sticking everything together. After a couple of hours I finally had
everything in the right place, so with much anticipation I pressed the
'on' button. 'Hmmmm...' I thought, 'that button used to turn my
computer on...'. Something wasn't quite right so I yanked the side of
the case off and tried switching it on again. Curiously enough the
computer seemed to momentarily jump into life (CPU fan started
turning, hard drive started to spin up etc) but after about half a
second it powered itself off again.

I stripped everything out of the case, so that the only things I had
attached to one another were the motherboard, RAM, CPU and a graphics
card. I tried turning it on, but it just did the same thing again (CPU
fan spins for about a half a second before stopping abruptly). The RAM
and graphics card are definately working as I've tested them in
another machine.

I've put a few computers together before, but I've never seen a
problem like this before. My best guess is that the mobo is faulty,
but I've got no way to verify this as I can't test the CPU and
motherboard independently of one another.

Does anyone have any ideas about what the problem might be?

Thanks, Richard.

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Richard George wrote:

Hi,

everything in the right place, so with much anticipation I pressed the
'on' button. 'Hmmmm...' I thought, 'that button used to turn my
computer on...'. Something wasn't quite right so I yanked the side of
the case off and tried switching it on again. Curiously enough the
computer seemed to momentarily jump into life (CPU fan started
turning, hard drive started to spin up etc) but after about half a
second it powered itself off again.

I've put a few computers together before, but I've never seen a
problem like this before. My best guess is that the mobo is faulty,
but I've got no way to verify this as I can't test the CPU and
motherboard independently of one another.

Does anyone have any ideas about what the problem might be?

Thanks, Richard.

Very likely that you have a short circuit between the bottom of the
motherboard and the metal standoffs on which the board sits.

Remove the board from the computer and place it on a non-conducting surface:
wood, cardboard, heavy paper as examples.

Half-inch wood or plastic is preferred as the height will alow you to plug
in the video card for the testing period.

Plug in the power supply cable to the motherboard (you may need an
extension), connect the keyboard, and a monitor.

Power up the system.

The board should power up.

If it does try placing a small piece of black electrical tape about one inch
square over each of the desired mounting holes on the underside of the
board.

Re-install the board in the case with the tape squares in place and poke the
mounting screws through the tape squares to complete the mounting.

Your system should power up correctly.

- --
Ron n1zhi

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Does anyone have any ideas about what the problem might be?

Thanks, Richard.

Yes.
The first thing I would check is that you don't have a short around
the screw holes of the motherboard. The power supply will check, and
if it finds a ground where there isn't supposed to be, it will not go.

You can see what happens when an ATX power supply is (or isn't) hooked
up correctly at my website, at the following address:

Well, site is down so can't get the exact address. Anyway, its at
http://www.aaronaxvig.tk under the Tech Mods computer section. Here
is a brief summary:

On the connector with many (20?) plugs, you need to basically supply
5V to the PS-On pin, which has a green wire. To get the 5V to it,
just connect it to one of the 5V pins on the same plug; find one of
the red ones. Put a wire between the two, and your power supply will
work. To see the pinout:
http://xtronics.com/reference/atx_pinout.htm

Anyway, back to the real problem. Note that if you connect a
powersupply to power without that little "jumper" in there, the fan
will just momentarily flick. I think that is your symptom, no? So,
maybe put spacers around screw holes on motherboard, or something.

Aaron

Hi Ron,

Thanks for your reply. I've now tried taking the motherboard out and
placing it on a big book. The CPU, RAM, graphics card and keyboard are
all plugged in but alas it's doing the same thing.

Any more ideas before I return the motherboard?

Thanks, Richard.

Ron Cook wrote in message ...
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Hash: SHA1

Richard George wrote:

Hi,

everything in the right place, so with much anticipation I pressed the
'on' button. 'Hmmmm...' I thought, 'that button used to turn my
computer on...'. Something wasn't quite right so I yanked the side of
the case off and tried switching it on again. Curiously enough the
computer seemed to momentarily jump into life (CPU fan started
turning, hard drive started to spin up etc) but after about half a
second it powered itself off again.

I've put a few computers together before, but I've never seen a
problem like this before. My best guess is that the mobo is faulty,
but I've got no way to verify this as I can't test the CPU and
motherboard independently of one another.

Does anyone have any ideas about what the problem might be?

Thanks, Richard.

Very likely that you have a short circuit between the bottom of the
motherboard and the metal standoffs on which the board sits.

Remove the board from the computer and place it on a non-conducting surface:
wood, cardboard, heavy paper as examples.

Half-inch wood or plastic is preferred as the height will alow you to plug
in the video card for the testing period.

Plug in the power supply cable to the motherboard (you may need an
extension), connect the keyboard, and a monitor.

Power up the system.

The board should power up.

If it does try placing a small piece of black electrical tape about one inch
square over each of the desired mounting holes on the underside of the
board.

Re-install the board in the case with the tape squares in place and poke the
mounting screws through the tape squares to complete the mounting.

Your system should power up correctly.

- --
Ron n1zhi

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Well, I've found the problem.

In my galactic stupidity I failed to read the section in the manual
that describes the "other" power cable that needs to be plugged into
the motherboard. Apparently lots of modern motherboards need two power
connectors, as they draw more current than a standard ATX power cable
can supply.

So I guess the lesson here is read the manual...

Thanks for your help!

Richard.

(Aaron) wrote in message . com...
Does anyone have any ideas about what the problem might be?

Thanks, Richard.

Yes.
The first thing I would check is that you don't have a short around
the screw holes of the motherboard. The power supply will check, and
if it finds a ground where there isn't supposed to be, it will not go.

You can see what happens when an ATX power supply is (or isn't) hooked
up correctly at my website, at the following address:

Well, site is down so can't get the exact address. Anyway, its at
http://www.aaronaxvig.tk under the Tech Mods computer section. Here
is a brief summary:

On the connector with many (20?) plugs, you need to basically supply
5V to the PS-On pin, which has a green wire. To get the 5V to it,
just connect it to one of the 5V pins on the same plug; find one of
the red ones. Put a wire between the two, and your power supply will
work. To see the pinout:
http://xtronics.com/reference/atx_pinout.htm

Anyway, back to the real problem. Note that if you connect a
powersupply to power without that little "jumper" in there, the fan
will just momentarily flick. I think that is your symptom, no? So,
maybe put spacers around screw holes on motherboard, or something.

Aaron